Chlorine dioxide (ClO2) has many industrial and municipal uses. When produced and handled properly, ClO2 is an effective and powerful biocide, disinfectant and oxidizer.
ClO2 is extensively used in the pulp and paper industry as a bleaching agent, but is gaining further support in such areas as disinfection in municipal water treatment. Other applications can include use as a disinfectant in the food and beverage industries, wastewater treatment, industrial water treatment, cleaning and disinfection of medical wastes, textile bleaching, odor control for the rendering industry, circuit board cleansing in the electronics industry, and uses in the oil and gas industry.
In water treatment applications, ClO2 is primarily used as a disinfectant for surface waters with odor and taste problems. It is an effective biocide at low concentrations and over a wide pH range. ClO2 is desirable because when it reacts with an organism in water, chlorite results, which studies have shown poses no significant adverse risk to human health. The use of chlorine, on the other hand, can result in the creation of chlorinated organic compounds when treating water. Chlorinated compounds are suspected to increase cancer risk.
Producing ClO2 gas for use in a chlorine dioxide water treatment process is desirable because there is greater assurance of ClO2 purity when in the gas phase. ClO2 is, however, unstable in the gas phase and will readily undergo decomposition into chlorine gas (Cl2), oxygen gas (O2), and heat. The high reactivity of ClO2 generally requires that it be produced and used at the same location. ClO2 is, however, soluble and stable in an aqueous solution.
ClO2 can be prepared by a number of ways, generally through a reaction involving either chlorite (ClO2−) or chlorate (ClO3−) solutions. The ClO2 created through such a reaction is often refined to generate ClO2 gas for use in the water treatment process. The ClO2 gas is then typically educed into the water selected for treatment. Eduction occurs where the ClO2 gas, in combination with air, is mixed with the water selected for treatment.
For many water treatment systems, the eduction process satisfactorily introduces ClO2 gas directly into the process water. Problems can occur, however, with such water treatment systems. One problem can occur when air is simultaneously introduced into a water system while educing the ClO2 gas. A tremendous corrosion potential results because oxygen from the air is added into the system. Another problem can occur when introducing ClO2 gas into a pressurized water system. Treating water in pressurized systems can be difficult when using educed ClO2 gas, since high-pressure booster pumps may be needed along with high-performance eductors. This not only increases cost, but also raises maintenance concerns, since high-performance eduction systems can be unreliable as operating pressures near 30 to 50 pounds per square inch (psi) or above (206.8 to 344.7 kilopascal (kPa) or above).
A need exists for a reliable chlorine dioxide generator that allows ClO2 to be introduced into pressurized water systems. Furthermore, a need exists for a chlorine dioxide generator that reduces or minimizes the potential for corrosion problems that can be associated with water systems.